Abstract

Purpose

Little is known about why the attenuation of heat loss responses with aging begins in the lower limbs. This study sought to determine whether passive heating causes the age-related decrease and limb-specific difference of blood flow (BF) responses between conduit brachial and femoral arteries, which are related to differences of cutaneous vascular conductance (CVC) between the upper and lower limbs.

Method

In 15 older and 12 younger males, BF in the brachial and femoral arteries was ultrasonically measured and CVC in the forearm and thigh was assessed during lower leg immersion in hot water at 42 °C (ambient temperature: 30 °C, relative humidity: 45%) for 40 min.

Results

The increased BF of brachial artery at the end of passive heating was similar between both age groups (older: 140 ± 4%; younger: 146 ± 11%), while that of femoral artery was smaller in older than younger group (119 ± 4% vs. 166 ± 11%, P < 0.01). Moreover, the increased CVC in the forearm was similar between the age groups (older: 356 ± 50%; younger: 308 ± 46%), although CVC in the thigh was significantly lower in older than younger group (303 ± 33% vs. 427 ± 51%, P < 0.05). These results corresponded to the BF responses of the brachial and femoral arteries, respectively.

Conclusion

These results indicate that age-related decrease and limb-specific difference occur also in conduit arteries of arm and leg, which might be related to the different reduction in CVC between forearm and thigh.

Notes

Acknowledgements

This research was supported by a grant from the Japan Society for the Promotion of Science, and a Grant-in-Aid for Scientific Research (No. 16207022 and No. 16H04851). We are grateful to the subjects who volunteered to participate in this study.

Author contributions

AO analyzed data and wrote the manuscript. CA, RO and TI-K conducted experiments and analyzed data. NK provided advice on the data about thermoregulation. YI conceived and designed research. All authors read and approved the manuscript.